parallelograms have equal lengths on opposite sides. in this picture, y is alone. Opposite of that, the length is 11. so y must be 11. the only choice there is A.
If you add 690 ml of water you will obtain 1.690 liter of 70% alcohol. Of course if you halve the amounts, e.g. 0.5 liter 75% alcohol and 345 ml of water, you will also obtain 45% alcohol solution.
